Blocks of nothing

This is something I’ve been encountering rarely, but often enough that I think it’s a random encounter that isn’t loading right or something. I’ve encountered sectors of map (the most recent one being 12 x 12 in size) where nothing exists. I examined the space, and it labels the ground as “nothing”, movement speed 100. Am I right in thinking this is a random encounter that glitched out?

It’s also diggable. I think I’m going to take some of this nothing home with me, and I’m going to spread it all over my lawn. Then guests could say “you have nothing in your lawn”.

I’ve also just found a 12x12 patch of “nothing”. Running GIT from 2013/05/01 01:52:59